text:
Flow separation in inviscid flow
I watched this video about CFD (

) where flow was assumed to be incompressible and inviscid, but how can vorticies occur behind the ball at the start of the video, shouldn't air in case of inviscid flow smoothly leave the ball

Euler CFD solutions are subject to something called artificial (or numerical) viscosity.  How much you have depends on whether your method is odd or even order -- dictating whether a diffusive or dispersive error term dominates.
(sometimes more artificial viscosity is added to an Euler code, but even if you do nothing, there will be some).
This is what allows an Euler code to separate flow from a sharp corner -- instead of achieving infinite acceleration and staying attached like a potential flow code will do.
I believe the artificial viscosity plays a role in setting up a Von Karman Vortex Street in an otherwise inviscid simulation.

Does numerical viscosity have the potential to be used to estimate pressure drag? In other words, does numerical viscosity have some physical background?

In certain cases, where the separation point is easy to predict (such as a flat aft face, or reasonably sharp corners), then yes, it will get the base drag reasonably correct.  However, for something like a cylinder or a streamlined body (with separation), it will likely get the separation point wrong and will therefore mispredict the separation drag.

This is a well known phenomenon, a Kármán vortex street.  Wikipedia explains it adequately.  I won't quote that entire article, though, daring for now to post a link-only answer.

Wikipeida says that such vortex can take place only with a specific range of Re numbers, but in the case of inviscide flow, the Re number approaches infinity. I am not sure about this because I was not able to find any mentions of the invisvid case in this article.

Vortices can form in Re=oo superfluids such as 3He, but the descriptions of that are way beyond me.  The Physics SE may be a better place to ask.


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What are the effects of wing washout and anhedral on induced drag?
I am studying for my ATPL and was curious if and how induced drag varies based on wing anhedral and geometric washout.
I have a basic understanding that spanwise flow affects induced drag since there's a tendency for pressure to equalise at the wing tips (at least that's what they teach in ATPL training programs...) and was curious what happens to induced drag if it was restricted by geometric washout (where the wing root has a higher angle of incidence compared to the wing tip) and wing anhedral on low-wing aircraft. Do these wing characteristics make a difference?
Would appreciate any input, thank you very much!

This very good answer should answer your question

@sophit that is indeed a phenomenal answer, but I don't know I'd agree it's appropriate for this question. P. Kämpf's deep dive into the efficiency of wing tips is not targeted at discussing anhedral nor washout. Perhaps those experienced in the mathematics of fluids could extend his answer to this question. However, I don't think we can assume that that level of expertise is widespread, esp. as the OP admits to no more than "a basic understanding" gleaned from the ATPL coursework.

@KennSebesta: agreed. Maybe I should have written: the part regarding induced drag should answer your question

Thank you gents. Looks like I have a lot more to learn!

Anhedral on a low wing airplane risks scraping the wingtips.  Is that really what you meant?

Not really, I was thinking more about its effect on span-wise flow causing wingtip vortices, which I now have a somewhat better understanding of.

Induced drag is not really about spanwise flow.  It is about the spanwise load distribution.  The closer your spanwise load distribution is to elliptical, the lower your induced drag.
Washout will un-load the tips.  So, if your load distribution is super-elliptical at the tips, then washout will reduce induced drag.  However, if your load distribution is sub-elliptical at the tips, then washout will increase induced drag.
We also use washout to prevent tip stall.  If a wingtip is highly loaded, it is more likely to stall at the tips first -- which is bad.
The difference in these is that when we're talking about induced drag, we're looking at the load distribution $l=q\,c\,c_l$ in terms of lbs/ft.
However, when we're thinking about local stall, we're just thinking about the local lift coefficient $c_l$ and how it compares to the local $c_{l,\mathrm{max}}$.
Since $q$ (dynamic pressure) is the same across the wing, the difference between the two is the local chord $c$.  For induced drag, we care about the distribution of $c\,c_l$ being elliptical.  For stall, we care about local $c_l$ staying away from stall.
The sweep of the wing has a significant effect on the spanwise load distribution.  Sweep tends to load up the tips.
In addition, the amount of taper in the wing has a significant role to play.
Consequently, straight wings tend to have taper ratios of about 0.5 to 0.6 -- and swept wings tend to have taper ratios of 0.4 or less.

Thanks Rob! So if I understand correctly, by reducing load towards the wing tip we can reduce induced drag?

@NickM: "by reducing load towards the wing tip we can reduce induced drag?" That's not the whole picture. Induced drag is at a minimum when the spanwise lift distribution is elliptical. So the big picture is having an elliptical distribution and reducing lift at the tip is a part of this big picture. As a side note: obviously reducing induced drag doesn't imply that the total drag gets also reduced

@NickM When I said super-elliptical and sub-elliptical at the tip, I meant was the distribution locally higher or lower than an elliptical distribution.  If you want to minimize induced drag, you want to get as close to elliptical as possible.  Sometimes that requires increasing the tip load, other times it requires decreasing the tip load.  I.e. It depends on the situation.

Technically, all else being the same, adding anhedral (or dihedral) reduces span thereby reducing aspect ratio, also. This increases induced drag, albeit very slightly for typical angles.

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

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Can an aircraft transmit Mode C when Mode A is in STANDBY or OFF?
I am a software developer in the aviation industry, so I do apologize if my terminology is not correct. What I want to know is - are there any cases in which the aircraft's Mode A is switched to OFF or STANDBY and the aircraft is still able to transmit Mode C replies? Or will switching Mode A to OFF/STANDBY also automatically switch Mode C to OFF/STANDBY? Would there be any differences in this behavior in the US versus in Europe?

Who is writing your specifications?

No. Mode A/C ATCRBS transponders have to comply with local regulatory standards (TSO-C74d/RTCA DO-144A in the US, equivalent to JAA/EURACAE standards in the EU, or other local standards complying with ICAO Annex 10, Vol IV).
Basic operating modes for ATCRBS transponders are OFF/StandBy, Mode A, and ALT or Mode A/C. OFF is self explanatory. StandBy is a holdover from the days when vacuum tubes were used in the power amplifiers. Standby is functionally OFF, but provided power to the tubes for them to warm up so there was no delay when it was switched on. Mode A provides responses to only Mode A interrogations and does not reply to Mode C. The ALT mode is sometimes labeled Mode A/C as it provides both Mode A and Mode C replies. It is not possible to provide Mode C replies without responding to Mode A.
The real question would be why look at a Mode A/C transponder. Other than some small aircraft, most aircraft today are equipped with ATCRBS/Mode S transponders. They follow RTCA DO-181F or the equivalent EUROCAE or ICAO Annex 10 standard. Mode S provides support for TCAS (ACAS) as well as ADS-B out using the Mode S squitter.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


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How many exterior stencil lettering (marking out maintenance or critical flight parts) are there on a Delta 767-300?
I was wondering how many different stenciling areas are located on a Delta 767-300 and wanted to know general locations of each. Some examples include the markings of "Static Port" and the APU exhuast. If there is stencil markings of with 5 lines of text, photos would greatly be appreciated.


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How does jet fuel not spill out upon disconnecting from the wing's intake?
I was watching a refuel yesterday and I was wondering: what type of mechanism is in place, so that when the fuel hose is disconnected, no fuel spills out? (wondering since the hose is pointing upwards connecting under the wing). Some type of vacuum? What's this mechanism called?
Here's a picture to illustrate the situation I'm referring to:

[skyapron.net]

Hello jlo, welcome to aviation.stackexchange.com. Could you please provide [image attribution] for the image in your question?

I wonder why I never wondered this.  Great question, welcome!

The system is based on two elements:

The underwing coupling is closed by a spring-loaded lid which can be pushed up to open the tank fuel line.

The refueling nozzle has a poppet valve which interrupts the fuel flow and when moved out allows the fuel to leave the nozzle, and pushes the tank coupling lid, allowing fuel to flow to the tank.

This is the general design and mode of operation:

Source.
Now if we focus on the nozzle:

Source (fuel exits at the bottom).
The poppet valve is at the level of the red annular bumper, and looks like this:

Source.
The poppet has number 15 below, and is resting on seal 43 until the nozzle is locked:

This ensures fuel cannot exit the nozzle prior the nozzle is locked, and after it is unlocked:

Source.
Handle 14 is used to lock the system and open the poppet with link 34 and shaft 32.

Another model:

Source.

In action
See that in action on this video. Note how the nozzle is first rotated with the ring handle after it is hung to the underwing intake, and then the smaller locking handle is operated to allow the fuel to flow. The same is done when disconnecting the nozzle, in reverse order.

If I understand the diagram, the poppet valve is in the filling nozzle.  How does that keep fuel that might be above the poppet valve from being spilled when the nozzle is removed?

@WayneConrad: There is no space between the poppet in closed position and the wing coupling wall. The nozzle goes into the coupling and when the poppet is opened it pushes to open the tank fuel line. More visible on this diagram.

I think I understand: There's a spring-loaded valve in the wing that is pushed open by the filling nozzle, but closed before the filling nozzle is removed.  And the design minimizes the space between the part of the nozzle that pushes the wing's valve open and the bottom of the wing's valve, leaving no place for fuel to be spilled from when the nozzle is removed.


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Alaska Airlines 737-9 MAX door plug row?
What row is the door plug, that detached during flight 1282, located near on an Alaska Airlines 737-9 MAX?

This New York Times article shows it as row 26.

I was watching Blancoliro's channel and his description. and it's like any lift out style plug door. There were supposed to be stop bolts installed in the roller tracks at the top so the door couldn't be manually opened or removed, but I don't see how even with those bolts missing the door could find its way up on its own. As soon as the pre-pressurization sequence starts on the takeoff roll, if it's half or one psi, that's up to a ton or so pushing on the thing to hold it where it is. At 14000 ft the cabin is about 5 psi, so maybe 10 tons plus. It's a strange story.


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Where can i find detailed dimensions of an aircraft?
I am doing a University project that analyses an aircraft aerodynamics. And to do that i need to replicate an aircraft in AutoCAD, then do a simulation.
Is there a public source where i can find the specific dimensions of an aircraft(nothing specific)?
I'm grateful for any insights you can provide on this, and thank you for your time and consideration.

An airplane is much more than its length, weight, and wingspan.  How deep will the analysis be?  Will you need moments of inertia, airfoil names, wing stiffness, control surface deflections, attributes of the turbine or piston engine or propellor(s)?

Currently i am concerned only with the physical dimensions, that include the airfoil name, whatever help me design the body of the aircraft

Resource location questions are not on-topic on this forum.

Length is easy to find. Contour, slope etc are harder. How detailed you need?

"where i can find the specific dimensions of an aircraft (nothing specific)?  Well, that clears it right up...

If this is ignoring aerodynamics, only about reconstructing the shape of an airplane from drawings and numbers, then this question might be better for https://stackoverflow.com/questions/tagged/3d-modelling.  Googling for "3 view" finds many drawings, e.g. https://commons.wikimedia.org/wiki/Category:3-view_orthographic_projections_of_aircraft.

Do a Google Image search for the name of the aircraft with "3 view drawing" in the search field.
Also, consult The Incomplete Guide To Airfoil Usage to possibly get a clue to the airfoil used.
Beyond that, consult "Janes All the World's Aircraft" -- your University library should have a copy.  The library is the old building nobody uses with all the books in it.

+1 just because the last sentence made me laugh!

Exactly how detailed do you need?  Basic information can be obtained from a manufacturers database. More detailed information may be found in an aircraft flight manual or aircraft maintenance manuals.  Some manufacturers offer quick reference guides and product review sheets, which contains specifications. This products are typically only available to serious buyers; not typically public available from a website or anything.


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What is the precision of the Fuel Quantity Indication System (FQIS) of the Boeing 777?
What is the precision of the Boeing 777-300ER ultrasonic FQIS? If for example it is 2% when 100 tonnes of fuel are loaded, there could be anything between 98 tonnes and 102 tonnes. How is this accounted for in the MTOW calculation?

This is an interesting question. However I think the quantity of fuel loaded comes from the fuelling system (truck or underground delivery). Then again, they of course have their own tolerances...

@Jpe61 I don't think so. AFAIK you set a target fuel on the refueling panel of the aircraft and it automatically controls fuel flow and distribution until reaching that target. It will obviously use the onboard FQIS to measure fuel amounts. Even if a predetermined amount of fuel is added, you would calculate that amount based on fuel remaining in the tanks, so again using the FQIS.

Roger that @Bianfable! Do you crosscheck the fuel ordered/delivered with what the previous flight left and FQIS?

FQIS accuracy is plus/minus 1 percent at full scale (main tanks) and 0
to 0.5 percent below 10 percent (center tank).

Source: https://www.federalregister.gov/documents/2019/10/10/2019-22150/airworthiness-directives-the-boeing-company-airplanes
Regrading MTOW, the FQIS accuracy is already considered in the system-level analysis that brings to a MTOW which is under-estimated by some safety-margin.

So by reading the document, here is my understanding:
At Full Scale ±1%
Full Main + less than 10% in CWT ±0 to 0.5%
Full Main Only ±2% (1276/63800 lbs in %)
Regarding MTOW, I don't know of any system-level analysis installed on the B77W could please be a little more specific on how this system works?


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How to design propellers for a contra-rotating system?
Supposing that the thrust requirement and the engine power and RPM are known, is there a way to estimate the propeller diameter and pitch for a contra-rotating arrangement (co-axial)? Also, If both propellers spin with the same RPM, and have the same diameter, how will the pitch change?

Are these contra-rotating propellers also co-axial? They need not be - e.g A400M

Yes, I want to calculate the propeller diameter and pitch if they are co-axial.

Two [non-expert] questions:  1) you'll have an upper limit on diameter for tip speed, right?  2) for conceptual level design sizing, couldn't you treat it like a single prop but just add a handful of % efficiency?

To put it another way, will the thrust produced by a contra-rotating (co-axial) propeller (e.g. two 30"x12.8" props, both spinning at 5000 RPM) be (nearly) double of that produced by a single 30"x12.8" prop spinning at 5000 RPM?


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Is induced drag only created by wingtip vortices induced downwash?
In PHAK, I saw that There is two types of downwash

formed by airfoil shape that necessary(help?) to produce lift
formed by wingtip vortices

in phak 5-7 It said 'This induced downwash has nothing in common with the downwash that is necessary to produce lift'
My question is
Does first type of downwash (necessary to produce lift) also produce induced drag?
I keep searching about this and they always say about wingtip vortices induce downwash not that 'necessary to produce lift' downwash.

"PHAK" is full of garbage.  I'll get back to you later with some specific examples.

I really don't know why they waste time and effort in the "PHAK" writing and teaching this stuff.
Fundamental in aviation is that the moving aircraft interacts with the air, producing drag.  Heavier than air craft must make lift to counter-act gravitional force.
This is done by increasing angle of attack from a zero lift state,
AKA D0.  Any drag associated with lift production is Dinduced, or Di.

Drag = D0 + Di

Downwash and tip vorticies are the result of lift production.  To say they are unrelated is nonsense.
Downwash is flow from the trailing edge.  In the simplest explanation, the mass of air pushed down = the weight of air craft
pushed up.
Tip vortexes form because increasing angle of attack (creating lift) causes a pressure differential between upper and lower wing.
The lift equation is:

Lift = Area × Density × Lift coefficient (including AoA) × Velocity$^2$

When velocity is high and AoA is lower, these tip vorticies can spill harmlessly away from the wing tip and not affect lift or drag.  When the plane slows down and AoA increases, the vortex may start to impinge on the upper wingtip surface$^1$.
So, the answer is that neither downwash or tip vorticies produce drag.  They are the result of the velocity and angle of attack one flys their aircraft at.
The most important concept to grasp is that the best combination of Velocity and Angle of Attack is at Vbg.  That's where one wants to be if the engine fails and a safe landing area is available to glide to.
$^1$ this has a secondary effect.  The aircraft must increase AoA or speed to maintain lift, resulting in more drag, directly translating into more fuel consumption.

There is a very common form of incorrect reasoning on display here. In a steady flow we observe two apparently distinct phenomena A and B. We then ask which is cause and which effect. This is almost always wrong, because usually both A and B are effects of causes that operated before the flow became steady. @Robert DiGiovanni is correct to consider how the flow evolves starting with zero lift. To say that "these tip vortices can spill harmlessly away from the wing tip and not affect lift or drag" is however seriously misleading.
A and B here are what are often called the bound vorticity and the free vorticity. Vorticity is a vector whose direction is the local spin axis of the fluid, and whose magnitude is the spin intensity. Mathematically, the
vorticity can be deuced from the velocity, and usually the velocity can also be deduced from the vorticity. They are alternative descriptions of the flow. Therefore we can pretend that either of them is the cause and the other the effect. This will not be a problem as long as we only consider steady flows.
So we can imagine that the trailing vortices, rather than "spilling harmlessly away", "reach back" to affect the velocity on the wing. This is "induced incidence" and is the "cause" of "induced drag". This mechanism is reduced for high aspect-ratio wings and is absent for two-dimensional wings.
The statement in PHAK that "A has nothing in common with B" is completely
ridiculous scientifically. Its only possible purpose is to prevent pilots from worrying about things they have no reason to worry about. In fact classical wing theory is a well-established university-level subject that is found hard by many students because it gets quite mathematical, but leads to many fascinating conclusions. For those who are merely curious, a description that I am assuming to be true of @aviii there should still be satisfying explanations. Let me try.
The purpose of a wing is to produce downwash, and the simplest explanation is indeed that "the mass of air pushed down = the weight of air craft pushed up". A fuller analysis of the vertical momentum also includes the pressure, which changes with velocity according to Bernouilli's Law. Just behind the wing, there is "lifting downwash" produced by the pressure
difference needed to achieve lift, and also "induced downwash" produced by (or at least associated with) the trailing vortices. In sum, these must combine to conform with the geometry of the wing, so the presence of induced downwash reduces the lifting downwash and therefore reduces the lift. It also results in drag.
I hope this helps but there are better explanations available. I could recommend one if I knew more about your level of interest.

in all fairness I did mention that, at lower speeds and higher angles of attack, the vortex can affect lift production.  I suggest it is in poor taste to mention my name and say my work is "seriously misleading".  This type of comment is unnecessary.

If you look at the wingtips of albatross and compare them with eagles you may gain some insight into what wingtip design is best for what combination of velocity and Angle of Attack works best for lowest drag.  Eagle wings have slats to gain as much energy from wingtip circulation as possible, whereas as smooth taper serves the albatross well.  Wingtip devices such as winglets can add drag at higher speeds (and also indirectly add drag through increased weight).

@Robert DiGiovanni. I thought you did a great job moving things on from the PHAK statement, but to move things on further it really is necessary to recognize that the vortices do much more than trail away. I was sure that you knew this and had simply been a little casual with your phrasing. I apologise for not phrasing this more respectfully.

how much the tip vorticies do (in terms of lift reduction) depends on Velocity, AoA, and tip design.  Your answer otherwise makes good reading.  The concept of trailing flow "reaching back" (flow reversal) is exactly what happens along the trailing edge as AoA approaches stall, and the tip vortex indeed has a similar effect from the side (at the tip).  Downwash at the tips and winglets can reduce this, as does higher AR, as you pointed out.

PHAK is actually not totally wrong:

In PHAK, I saw that there are two types of downwash

formed by airfoil shape that is necessary (help?) to produce lift
formed by wingtip vortices

This is correct.
In aerodynamics there are indeed two distinct phenomena called with the same name i.e. downwash. The first one is a pure 2D phenomenon while the second one is a 3D phenomenon.

Let's start considering a 2D "wing" i.e. an airfoil. The airflow around an airfoil is well known and looks like this:

(Source)
Schematically, the airflow goes up in front of the airfoil, accelerates on its upper part, goes down behind it and decelerates on the lower part. If the freestream airflow's speed could be subtracted, a "circulation" of air around the airfoil would be visible:

(Source: Daniel P. Raymer, Aircraft Design: A Conceptual Approach)
This circulation of air is what creates lift on the airfoil. The airflow going up in front of the airfoil is termed upwash, while the air going down behind it is called downwash.This is the first downwash and it is jointly-responsible for the creation of lift (together with the upwash, the acceleration on the top and the deceleration on the bottom). Mathematically all this is translated via the famous Kutta–Joukowski theorem:
$L=\rho V \Gamma$
where $\Gamma$ (gamma) is the mathematical symbol used to represent the circulation.

For the second downwash we have to go 3D and bring into play Newton's third law (action-reaction): in order for the air to push the wing up, the wing must push air down. That means that if well in front of the wing the airflow is basically horizontal, on the back it is slightly going downward. This downward movement is also called downwash and is associated with the induced drag.
Note that in 2D the airflow is horizontal both well in front and in the back of the airfoil, is the circulation (first downwash) around the airfoil that produces the lift and there's no second downwash i.e. no induced drag in 2D (there's only lift).

Does first type of downwash (necessary to produce lift) also produce induced drag?

Yes, they are the two sides of the same coin. It can be demonstrated that the second downwash (the one responsible for the induced drag) is proportional to the spanwise change of lift i.e. the spanwise change of circulation i.e. the spanwise change of the first downwash (the one responsible for the lift). It can also be demonstrated that the induced drag reaches a minimum if the spanwise change of lift is elliptic.

This is a very well written answer.  Could you expound upon "in 2D (there's only lift)?  One might say (in a infinitely small 2D cross-section) there is neither lift nor drag.  Then it is confirmed that the "first type of downwash also produces induced drag", finishing with elliptic distribution minimizes induced drag.  Why are we "beating around the bush" with induced drag when you so well illustrated it simply as a rearward pointing vector combined with the normal lifting force vector (from the aerodynamic force generated by the wing with increased AoA from D0) in a previous answer.


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Circling aircraft
Hi guys I'm a newbie here, so apologise if this has already been answered. I'm in The UK and since 2020 RAF aircraft have been circling my city, and have noticed after that it is happening in other parts of UK. They are quite often Eurofighter Typhoons. I'm not talking refuelling patterns, circles or variations of directly above the city. I'm seeing them on radar websites, which I understand can be iffy, but I can very much hear and often see them, so they are determinedly covering the area. This has involved numbers of them, I've seen 7 listed on radar with individual call signs, and sometimes multiple times a day. As it's mainland UK can't see why it would be surveillance, radar, or command and control. I've considered backup for coastal rescue, but it happens far too frequently, and I've seen similar activity over inland settlements. I would think it is also a bit weird for training to have close proximity multiple aircraft to buzz over a city. Also, the same aircraft can stay up to about half hour so suggest that's a bit long for waypoint behaviour. Thank you for any input as it's confusing me now.

Unless you provide a screenshot of a tracking site, or a registration number which points to a specific example, it is not possible to answer, only to provide opinions which is not helpful.

How do fighter pilots maintain their edge? How do they stay "good"?
Practice practice practice. Those are not on operational missions, just practice.
Having a good aircraft is only part of the equation. The pilot must also be good.
I see the same here over coastal Virginia (USA). Or, on FR24, over Kansas City. Or near Las Vegas.
Or these guys near Tuscon AZ, on a quiet Thursday morning.

(from FlightRadar24)

Hi, thank you for your reply. That is the pretty much one of the few conclusions I can come to, but I'm not sure why they stay over the city for sometimes up to half hour.

Maybe, @YorkshireRover, they're practicing spotting ground targets within a city. It's easy to pick out a city from the countryside, but it's harder to pick out Bob's Munitions Factory when it's sitting next to Annie's Pretzles & Pickles. Learning to spot ground targets from the air is good, even with all the high tech gizmos on today's fighter aircraft.

@FreeMan Thank you for taking the time to respond, and that sounds like the most likely answer to me.


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Can VANS RV-12 with Rotax 912 ULS be used/equiped in IFR?
May an instrument rated pilot fly a VANS RV-12 with a Rotax 912 ULS with the following equipment in VMC, under instrument flight rules for IFR training?

Dynon 10" HDX Touch Screen Primary Display
Dynon Autopilot Control Panel SV-AP-Panel
Dynon Knob Control Panel SV-Knob-Panel
Dynon ADSB In/Out
Dynon Remote Mount Transponder
Garmin GTR200 Comm Radio

Also, is it possible to re-certify it for IFR use? If yes, what additional equipment is required?

According to which regulations? FAA, UK CAA, EASA, some other country?

Is that the only equipment it has??


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Takeoff-chart Interpolating Numbers from a range
I'm studying for my AIRAT (Instructor Written) in Canada using Nizus, but I've always had trouble answering the questions about takeoff distances at 27 ºC when given a chart with 20 ºC and 30 ºC, even since the start of PPL. I want to understand it properly so I can effectively teach my students who have troubles with it.
The question is a two-parter, first calculating a takeoff distance with the following values:

Parameter
Value

Airport Temp
30 ºC

Airport Elevation
3000' AMSL

Altimeter
30.92 inHg

Wind
10 kt tailwind

Flaps
10º

Runway
Dry grass

With a pressure altitude of 2089', the nearest values are the 2000' and 3000'. I used the 2000' line of the chart.
At 2000' at 20 ºC the ground roll is 1080' and the total to clear a 50' obstacle is 1895'.
At 30 ºC it's 1155' and 2030'.
The chart says it's configured as follows: 2300 lbs, flaps 10, full power prior to brake release on a paved level dry runway with no wind. The notes state:
Headwind subtract 10% per 9kts
Tailwind add 10% every 2kts up to 10kts
Dry, Grass Runway or Gravel add 15% to ground roll.
At 30 ºC I calculate my takeoff distance being 3305'.

The second part asks by how much the takeoff distance will decrease if the temperature drops to 27 ºC.
I'm doing something wrong here as I calculate it to be 3250', with a distance change of 55', but that isn't an available answer.
How do I get the proper numbers to use at 27 ºC?

this is the chart here https://i.imgur.com/9HnYWR3.png, the first question https://i.imgur.com/IGZSMxP.png, and the second https://i.imgur.com/kkKLH1p.png

Is your question really just about how to properly interpolate or is it more than that?

If the reference question was designed to see how well you can interpolate then I’d think you’d need to interpolate for both temperature and pressure.

In order to get the exact answer I'm sure you'd need to interpolate for 2089' too I guess, but I originally figured it'd be such a small difference at that scale that there'd be no need. For 27degC I originally found the numbers for 25 by adding em both together, divide by 2, then add the number for 30degC again and divide by 2. I figured that'd get me to 27.5degC, but maybe that's not how that works at all?
And I appreciate you guys taking the time to help me work this out.

I have an ASA CX-3 Flight Computer and that's what it gives, though I've never understood how this works out pressure alt as when I do it for personal flight calcs I've always just done 29.92 - 30.92 = -1 * 1000 = -1000.

See this answer for a more precise formula to calculate pressure altitude.

I am getting a takeoff distance of 3,502' for a takeoff over 50 FT on a grass strip with a 10-kt tailwind.

2,030' * 1.5 * 1.15 = 3,502'

To interpolate you will need to figure out the percentage between the two temperatures.

(27-20) / (30-20) = 70%

We take the difference between the chart values for 20 and 30 degrees

3,502' - 3,267' = 235'

Multiply this value by the percentage

235 * .7 = 164.5'

Since we subtracted the 27 from the lower value we will add in this number ot the lower chart value

3,267 + 164.5 = 3,432

This is a difference of 70 feet.

Pressure altitude with Kollsman at 30.92 would be 3000 feet - 1000 feet = 2000 feet.  Dry grass only affects ground roll.
Distance to clear 50' obstacle at 30 C :   2030 feet
Ground roll distance:  1155 feet
30 C with 10 knot tailwind:  2030 × 1.50 = 3045 feet
Ground roll with tailwind: 1155 × 1.5 = 1732 feet
Ground roll with tailwind and grass: 1732 × 1.15 = 1992 feet
difference: 1992 - 1732 = 260 feet more

Total distance to clear 50' at 30 C: 3045 + 260 = 3305 feet

Distance to clear 50' obstacle at 20C:  1895 feet
Ground roll distance: 1080 feet
20C with 10 knot tailwind: 1895 × 1.5 = 2842 feet
Ground roll with tailwind: 1080 × 1.5 = 1621 feet
Ground roll with tailwind and grass: 1621 × 1.15 = 1864 feet
 difference: 1864 - 1621 = 243 feet more

Total distance to clear 50' at 20 C: 2842 + 243 = 3085 feet

  3305 - 3085 = 220 feet
  220 feet÷10C = 22 feet per degree

22 feet per degree × 3 C = around 66 feet less at 27  C

Answers of 3305 feet and 66 feet difference seem ok!


text:
Assuming a descent at 250kt IAS and idle thrust, will the resulting ROD be higher at a higher GW, or lower?
I was recently told by a pilot that it works in inverse order: Keeping indicated airspeed steady, and using idle thrust, the rate of descent will be lower with a higher gross weight (and a higher rate with a lower gross weight).
Somehow this does not make sense to me.

Yes, the answers and comments to this question explain the "why", thank you


text:
Question about go-around trajectory
What does ATC expect you to do if you go around on a visual approach, considering you were never cleared for an instrument approach? Do you set go-around altitude according to the instrument approach or to circuit altitude?

Does this answer your question? On a "Visual Approach", do I execute a "missed approach" or do I go around?

Could you clarify if your question is regarding flying VFR into a controlled airfield?

If you're in a visual approach flying VFR, you go around at circuit height and remain in the circuit.
If you're cleared for an instrument approach you would have been given missed approach procedure, or you follow the standard missed approach.
If in any doubt, ask. That's what they're there for.

As you called this a "circuit" and not a "pattern" I'm making an assumption you're flying in the UK. If I'm right, there's a couple of subtle hints there when you request joining info.
The standard phrasing goes something like:

[Station] Approach, G-ABCD, 10 miles south west, request join.
G-ABCD, [Station] Approach, QFE 1012, Runway 27 in use, right hand circuit, traffic is a Cessna 152 in the circuit and a PA-28 on a 4 mile final. Join overhead, Report entering the ATZ.

In bold are your two hints that the approach controller (in this example) is expecting you to enter the visual circuit. They have both told you the circuit direction, and given you some basic information about the traffic currently in or near the ATZ.

Your example seems to use a VFR pilot. I'm not sure if it's different outside of FAA-land, but within FAA-Land it is very clear that a "visual approach" is an IFR-specific procedure.

@randomhead A visual approach is an IFR-specific procedure in EASA-land as well :) Albeit one without a defined missed approach procedure, hence the original question

Yeah I've made a bold assumption here which might well be wrong.


text:
May an IFR aircraft be instructed to "squawk VFR" if it goes around while executing a visual approach?
A pilot on an IFR flight plan is executing a visual approach to a towered airport.
The pilot executes a go-around due to gusting winds and notifies the tower controller. The controller asks his intentions. He replies that he would like to make another attempt to land at the airport. The controller instructs: "Squawk VFR and enter a left downwind for runway 5."
Is the instruction to squawk VFR proper? Are the rules different under FAA/EASA/ICAO regulations?

Curious about what Class airspace it was.  I was reading Class D controllers only "use visual means to identify and separate aircraft".

Ryan, he intends to land after going around.  Robert, yes - tower controllers are primarily visual.

Were you on an IFR plan or simply shooting practice approaches?  It's somewhat "normal" if shooting practice approaches and you have not informed tower of your intent to do multiple approaches.  If you are on an IFR plan and did not agree to cancel IFR, it's unusual.

Voting to reopen after editing the question to clarify what I believe was OP's intent: by "requesting to land" the pilot means he is on the upwind leg, and is conveying that he wants to attempt another visual approach at the airport (instead of, e.g., diverting to an alternate airport).

No, that scenario does not sound normal to me. For one thing, a visual approach is an IFR procedure. Instructing the crew to change to a VFR squawk makes it sound like the controller is suddenly treating the flight as a VFR flight, which makes no sense. A controller is never allowed to just cancel IFR; going from IFR to VFR must always be explicitly requested by the crew ("cancelling my IFR flight"). We are not even allowed to suggest a flight to change to VFR, the idea has to come from the pilot.
Besides, it makes no sense that the controller would change the squawk code of a (presumably) already identified flight to a non-discreet code (1200/7000) since radar identification would then be lost and it would be impossibly to continue to provide radar service.
If the example you provide is a real one, there is obviously a reason for the controller doing what they did, however, based on the limited information you give here, it is hard to see what the reason would be. Maybe if we knew the whole picture, it would make more sense.

"We are not even allowed to suggest a flight to change to VFR" When landing at an non-towered airport in the US, Approach will ask if you have the field in sight and, if so, will tell you to cancel "with flight serivice on the ground or with me". You might argue the latter's technically not a suggestion to cancel now in the air, but that is how pilots interpret it in practice and, at least for GA, nearly always agree.

@StephenS Which makes sense, if you are landing at a VFR-only aerodrome (one with no instrument approach). You can't land there IFR. But that's not something enforced by ATC, that's an aerodrome specific restriction that you planned for yourself when you planned the flight.

@J.Hougaard Most public non-towered airports here have an RNAV approach these days, and many already had NDB, VOR or even ILS approaches, so you could stay IFR to the ground if you insist, but Approach will suggest canceling iff they clear you for the visual.

@J.Hougaard At least in the US, controllers will make the comment that Stephen mentioned even if the airport has instrument approaches. Many US airports have instrument approaches but no towers, meaning that the pilot has to cancel IFR himself. ATC can't release other IFR traffic into or out of the airport until they receive the cancellation so it's easier for everyone if pilots cancel when airborne if they can. But it's always the pilot's decision, not ATC's, as you said.

@Pondlife OK, I guess that's because the US has a slightly special way of dealing with IFR/VFR and opening and closing flightplans. See related: https://aviation.stackexchange.com/questions/35056/who-closes-an-airlines-ifr-flight-plan-and-when

@J. Hougaard, it looks like you may be a contoller in Scandanavia? Because your rules might be different... I am assuming that the original questions was from the U.S., but if I am wrong then your answer may be more appropriate.  Otherwise this is a common practice in the U.S. as I explained in my answer.

@MichaelHall I wonder why you would make the assumption, since there is nothing in the question to indicate that OP is wondering specifically about US procedures. As such, I have answered in accordance with common practices, not something related to any specific country.

@J Hougaard, I have my reasons for making this assumption, but I don’t think it is important to list them here.  My point is that I don’t agree that your answer reflects a global common practice.  Specifically, you mention that if the squawk code was changed “radar identification would be lost and it would be impossible to continue to provide radar service.”  However, radar service is not provided in the visual tower pattern, so if the pilot accepts a turn to downwind in the tower pattern it is apparent that radar services are no longer needed or wanted.

@MichaelHall I absolutely use radar as a tool for traffic in the visual circuit, and I also have IFR traffic in the circuit almost daily. I think most people would agree that the most common practice within aviation is one that complies with ICAO standards, which the FAA is notoriously bad at doing.

Fair enough, I can't dispute how you may use radar as a tower controller.  Admittedly most of my flight time is military, but I have ALWAYS been instructed to stop squaking whenever doing touch and goes in the VFR tower pattern.

@expeditedescent In the US, most class D tower controllers are not radar certified. Many D towers don’t even have a radar display, and those that do may officially only be allowed to use it to help them visually identify traffic. (Class B/C towers are different.) Things are weird over here.

I take issue with the idea that an aircraft has to be squawking a discrete code in order to be radar identified. This is categorically untrue in my (FAA) experience; one can even provide radar services to a radar-identified aircraft that does not have a transponder at all.

@randomhead Fair point. But assuming an aircraft was assigned a discrete code - in that case, the identification would most likely be based on that code, so if it were changed, identification would be lost (at least until another form of identification could be established)

@expedite, again I disagree. A discrete beacon code makes it easier for a system (whether an automated computer system or an "organic" air traffic controller) to track a target. But they can track and maintain the identity of any target shown on the scope, primary or secondary, whether squawking no code, a non-discrete code, or a discrete code. Would it require some work to re-enter the identification of the aircraft into the radar system? Probably. But a target squawking VFR does not mean the integrity of that radar target has been lost.

@randomhead I'm not talking about the radar track, I'm talking about the identification of that track. Legally, the identification would be lost - even if, practically, it maybe wouldn't

"Identification" in my vocabulary refers to the controller seeing a target on the scope and correlating that target with a particular pilot talking on the frequency. It is true that the automation system will no longer keep the datablock information on a track when the pilot squawks VFR, but the radar system will keeping tracking the target and radar identification will not be lost.

I understand why ATC can't unilaterally cancel IFR, but why would suggesting it be a problem?

@Someone Because the pilot might feel pressured into going VFR in marginal weather conditions

FAA answer.
No, the instruction to "Squawk VFR" (code 1200) would not be proper in this case. But there can be nuances.
First of all (and this is an extremely pedantic point), just because the controller said "Squawk VFR" does not mean they are no longer providing IFR separation. Yes, yes, of course it is a near-certainty that in this situation, the controller is telling the pilot to squawk VFR because they think the pilot wants to maintain VFR. But it is theoretically possible for a controller to maintain the radar identification of any aircraft squawking any code (or even no code at all, if there is sufficient primary radar coverage) and provide IFR separation to that target. Theoretically, of course.
So the real question is:

Is the controller correct in assuming that a pilot’s request to immediately return to the airport and attempt another landing, following a go-around while executing a missed approach, is a request to cancel IFR?

And again the answer is no, this would not be a correct assumption.
The phrase "cancel IFR" appears several times in the 7110.65. The most important one comes right at the beginning of the document, paragraph 2–1–4 Operational Priority:

NOTE-
It is solely the pilot's prerogative to cancel an IFR flight plan.

ATC is not allowed to solicit cancellation of IFR. The pilot must explicitly state that they wish to cancel their IFR flight plan, to which ATC's proper response is: "(Call sign) IFR CANCELLATION RECEIVED" (4–2–10b). If the pilot does not hear this stated, they are well within their rights to assume they are still on an IFR flight plan. The only exception to this is if the pilot of an IFR flight is performing an approach and, prior to completing the approach, requests to remain in the VFR traffic pattern upon completion. In this case the "flight" is terminated and the aircraft, which had been receiving IFR separation (see 4–8–11a1), will maintain VFR and stay with the Tower controller in the pattern (4–8–12). In this situation the controller saying "Squawk VFR" is purely a housekeeping task to make sure the radar scope reflects reality, namely, the aircraft was VFR as soon as they began the "go" portion of their touch-and-go.
An unplanned go-around by an aircraft executing a visual approach is handled differently. Paragraph 7–4–1 Visual Approach is the relevant rule, and the entire paragraph is germane to the discussion, so I have copied it below:

A visual approach is an ATC authorization for an aircraft on an IFR flight plan to proceed visually and clear of clouds to the airport of intended landing. A visual approach is not a standard instrument approach procedure and has no missed approach segment. An aircraft unable to complete a landing from a visual approach must be handled as any go-around and appropriate IFR separation must be provided until the aircraft lands or the pilot cancels their IFR flight plan.

a. At airports with an operating control tower, aircraft executing a go-around may be instructed to enter the traffic pattern for landing and an altitude assignment is not required. The pilot is expected to climb to pattern altitude and is required to maintain terrain and obstruction clearance. ATC must maintain applicable separation from other aircraft.
b. At airports without an operating control tower, aircraft executing a go-around are expected to complete a landing as soon as possible or contact ATC for further clearance. ATC must maintain separation from other IFR aircraft.

Notice the difference between a and b. At an untowered airport ATC will only provide separation between the go-around aircraft and other IFR aircraft, which is the only separation IFR aircraft ever receive in Class E airspace.
At a towered airport, ATC may instruct the aircraft to enter the tower pattern, and an altitude assignment is not necessary. The controller will provide "applicable" separation from other aircraft; what this means depends on when the the airspace is Class B, C, or D.
In this situation the aircraft is still IFR, despite being in the VFR traffic pattern. Their clearance limit was the destination airport, and it remains so; they were cleared for a visual approach, and they remain so cleared. They are maneuvering visually and clear of clouds for a landing on the assigned runway.
How the separation is maintained is up to the tower controller. They may call the approach controller and request that no arrivals be cleared for approaches to the airport, thereby effecting non-radar or procedural separation between the aircraft and any IFR arrivals. Or they could coordinate a radar point-out with the approach controller, thus putting the responsibility on them to keep their traffic farther than 3NM/1000' from the go-around aircraft. Or they could use visual separation, whether pilot-applied or tower-applied; visual separation is a valid form of IFR separation, so long as some other form of separation exists before and after the application of vis sep; this means the pilots must have each other in sight, or the controller must have both aircraft in sight, before the aircraft get within three miles of each other.
If the controller is unable to ensure applicable IFR separation, they can say so:

ATC: Unable IFR closed traffic due to IFR inbound. Say intentions.

Then the pilot must decide whether to explicitly say "We'll cancel IFR and enter the pattern" or "Request vectors for another approach."
In no situation should the controller assume the pilot wants to cancel IFR without hearing them say so in no uncertain terms.

You are typically not operating under IFR in the tower controlled traffic pattern if in the United States, so the short answer is yes.
It is not unusual at all to shoot an instrument approach to a runway, execute an option, (i.e. touch and go or low approach) and then turn downwind into the tower landing pattern.  Generally tower will ask you to squawk standby to declutter approach control’s scope.
It is correct that when cleared for a visual approach you are still on an IFR clearance.  However, what is imporant is the pilots specific words to the controller after aborting the landing:  If the pilot stated “missed approach” and began executing the IFR missed approach procedures he/she should expect to continue to be given IFR handling, i.e. vectors by the approach controller to set up for another instrument approach.  This is especially true if still talking on approach control’s frequency.
However, if the pilot is on tower frequency, weather is VMC and the tower pattern is open, and for fuel or other reasons the pilot desires to turn downwind immediately after aborting a landing, the request should be stated unambiguously:  For example something like, “Tower, N123WP going around, cancel IFR, request left/right closed traffic for landing”.  This makes the intention to remain VFR in the pattern to expedite landing clear, and approval from tower along with a request to change squawk would be entirely appropriate.
The pilot in this case stated "going around" and it sounds like tower made a reasonable assumption about intentions based on weather conditions and the fact that the pilot had previously requested visual to a full stop.  (Requesting an ILS approach to the option could imply multiple practice instrument approaches might be desired for training...)
If this is not what the pilot wanted, it needs to be rebuked clearly and immediately.  For example, “Negative, N123WP is executing the missed approach, request IFR vectors for another visual/ILS/RNAV approach runway 25.”
Instead the pilot accepted tower's clearance to turn downwind into the VFR pattern, and the change to a 1200 code was proper.

You may not be operating on a full set of IFR instructions (i.e. heading/route and locked-down altitude) but you should be afforded IFR separation in the traffic pattern, if the go-around was unintentional. Reference: 7–4–1 (a) and (b). Read between the lines for (a) and (b).
If you're shooting instrument approaches and request to terminate an approach with "option tower" that does imply cancellation of IFR after completing the option and you will be afforded VFR separation in the pattern.

@randomhead, I’m not quite sure what you are trying to say here.... What do you mean by “a full set of IFR instructions”?  And are you implying that both IFR and VFR can mingle in the tower traffic pattern, and tower controllers will be expected to manage them both somehow?

Late response, sorry. Yes, an aircraft executing an unplanned missed approach in VMC may enter the "VFR" traffic pattern for a runway and retain their IFR clearance despite not receiving IFR instructions (heading and altitude). This is dependent on traffic considerations; if there are other IFR inbounds ATC needs to maintain appropriate airborne separation (3NM), which may preclude this "traffic pattern" option and the a/c will instead be given a heading and altitude and shipped to departure. ATC will continue to provide runway separation between all aircraft (IFR and VFR) as normal.

If an IFR aircraft is coming in on an instrument approach and is planning on going around (or performing a touch-and-go) and then staying with Tower for pattern work, the IFR flight is considered completed, and IFR is automatically cancelled, upon completion of the approach. Then an instruction to "squawk VFR in the pattern" would be appropriate. But if the aircraft was supposed to be a full-stop landing and the missed approach was unplanned, ATC cannot cancel their IFR flight plan for them. [cont...]

The pilot could say something like "Going around, request to stay in the pattern" (which is not a request to cancel IFR). Then the controller might say "Roger, make [left/right] traffic" or they could say "Unable IFR closed traffic due to IFR inbound, say intentions." Then the pilot has to decide whether to explicitly cancel IFR and continue in the pattern VFR, or accept a heading and altitude for resequencing by Approach. Except for the situation of a planned T/G followed by pattern work, ATC cannot consider an IFR flight plan terminated until the pilot explicitly says "Cancel IFR."

@randomhead, I have never heard of co-mingling IFR and VFR traffic in the tower pattern.  That's not to say it isn't permissible, just that I have never observed it to happen and it goes against my paradigm of the tower pattern being VFR only.  Why might a pilot want to stay IFR once you have committed to flying the pattern?  How might a tower controller without radar ensure IFR separation is met?  And what might the IFR clearance and instructions on the upwind leg be?  (i.e. "cleared to ___ via visual approach, maintain pattern altitude"?)

Beyond my personal paradigm, IFR implies navigating primarily by reference to instruments, which doesn't really fit with flying the traditional pattern.  I'm not sure how to reconcile this...

It would be very rare, I agree, but the book says it's a possibility. The pilot may want to retain their IFR clearance because their OPSPEC says they can't cancel in the air, or any other reason. If the tower controller (whether with radar or not) can't ensure IFR separation they don't permit the operation in the first place. There would be no "clearance;" as 7–4–1 (linked above) says: "aircraft executing a go-around may ... enter the traffic pattern for landing and an altitude assignment is not required. The pilot is expected to climb to pattern altitude." The clearance limit is unchanged.

IFR implies navigating by reference to instruments, but in the traffic pattern the need for navigation is minimal; the pilot maneuvers by reference to the ground and maintains situational awareness via the big ol' window at the front of the plane, just as they did when coming in for a visual approach in the first place.

@randomhead, thanks for clarifying your point.

Since you were on an IFR visual approach and have "gone around" after your 1st landing attempt, and are in the landing pattern curcuit, weather permitting, why not do what the tower says?
There may be different procedures for IFR approaches and go arounds. They may have slotted you to "fit in" for left downwind for runway 5 VFR.  Switching (to 1200) and landing seems to get it done.  Unless you leave the landing pattern or do not follow their instructions, there does not seem to be any harm.

It would also help to be clear about approach (as flying into the towers airspace) as compared with being in the pattern and going around.

We were IFR and cleared for the visual approach.  Over the threshold and winds gusted strongly.  The PIC decided to go around, powered up and stopped his decent.  He then advised the tower he was "going around" (not "missed").  The Tower asked his intentions and he said he still wished land.  TheTower then said:  Okay squawk 12) and enter a left downwind and brought us around to land.  Those are the complete facts.

There are different procedures for aborting a landing if you are operating visually under IFR vs VFR that need to be clearly understood by instrument rated pilots.  This response doesn't really answer the question.


text:
If I am on flight following, do I have to be direct to my destination?
Can I ask for VFR flight following with waypoints to get to my destination, or does it have to be direct? (Heading changes needed to avoid sua, weather, etc.)

Related, possibly duplicate: How should I request flight following when I'm not taking a direct route to my destination?

ATC has relatively large "bubbles" they need to protect for around IFR aircraft—3 miles or 1000 feet at lower altitudes, 5 miles or 2000 feet at higher altitudes. Therefore IFR aircraft are given very explicit clearances on what route or heading to fly at what altitude.
ATC does not have nearly as much responsibility for separating VFR aircraft. Only in Class B airspace are VFR pilots afforded airborne separation between VFR and IFR aircraft, and only in Class C airspace are they afforded separation from IFR aircraft—and in Class C airspace the separation is "the dots on the screen don't touch." Quite a far cry from a three-mile bubble.
So VFR aircraft are allowed to navigate and maneuver as desired, at whatever altitude is desired, in accordance with safety of flight and following all applicable FARs. Unless ATC issues a specific instruction, such as "Fly heading 360" or "Maintain VFR at 4,500," you do not need to fly at any particular heading or altitude.
However, if you are navigating using pilotage or airways and not following the magenta line on your GPS, it would be appreciated if you mention that so the controller isn't concerned when they see you thirty miles and fifty degrees off of what they think is your "on course" track. When you request flight following the controller makes an entry into the system and generates a flight plan that only has two fixes on it: Departure airport direct to destination airport. If you are not flying a direct route, they will often have to update your position in the system to make the automated handoffs between facilities work properly, and they may as well use your actual route.

If you are asking how to inform the controller that you will not be direct to your destination, see this question and my answer to it.


text:
IFR training in the free route airspace
The free route airspace is spreading in Central Europe, consuming routes and decomissioning VORs. There are no routes left in the high airspace, and some of the FIRs keep a few low (up to FL95) RNAV routes while others don't have any at all. Some ground-based navaids were decommissioned too. That means any and all IFR flight requires GNSS-based RNAV capability.
Is the training syllabus for instrument license changed accordingly to assume the licensee will always fly an RNAV-capable aircraft as that's required everywhere in their home country, or is there some way to train VOR, DME and NDB-based non-RNAV procedures provided?

VOR, DME, NDB etc. are still used for approaches in many places, just not so much enroute

@expeditedescent I first thought that all the VORs were decomissioned, because skyvector started showing them grayed out and without the compass rose. But at least in Czechia the AIP still lists all the VORs as active and available for navigation, including the en-route ones, and the on-airport ones are used for VOR+DME approaches, though all STARs are RNAV.

Many VORs are decommissioned, but some VORs and DMEs need to stay to provide basic RNAV coverage


text:
Does a B777 have a control priority button?
There have been accidents where one pilot gets confused, panics, inappropriately pulls or pushes the control column, and the other pilot does not manage to get control from them and the aircraft either stalls or nosedives into the ground. Recent example is Atlas flight 3591, but there have been other airliner accidents, and Dan Gryder mentions it as probable cause of some training flight accidents.
Now in aircraft with mechanical controls, when opposing forces are applied to the control columns (including on the Atlas B767), they usually split and each half controls the respective aileron and half of elevator, which is rarely enough to recover. On the other hand on fly-by-wire Airbus, the non-confused pilot can simply press the control priority button and recover (the confused pilot is unlikely to press the button the necessary way to win a priority contest).
But a B777 has connected fly-by-wire control columns. Is there an emergency option to disconnect them and specify which one the aircraft should respond to?

Related: How does the Boeing 777's yoke of both the captain and the first officer have synchronized movement?

@Bianfable, that explains a lot of it, though a bit more detail on how it picks which side to then listen to would be welcome.

I just checked the FCOM and FCTM again. There is an entire chapter about "Jammed Flight Controls" in the FCTM, which describes the proper way to override the jammed controls. But it always assumes a jam, it does not cover the case of opposite inputs, which is what you are asking about. I can tell you that there is no control priority button to disable one yoke, but I am not sure what would happen in case of opposite inputs. Maybe Mike Sowsun (B777 pilot) will know...

I guess that would be an answer. As long as the confused pilot is pushing or pulling with all their might, it is indistinguishable from any other jam, and we probably won't know what happens when the jam is “cleared” (the plane breaks out of clouds and the confused pilot realizes they are pushing the wrong way) until somebody makes an AQP scenario out of the Atlas 3591 or similar accident.

BEA made an investigation after AF B777 had control desynchronized during an approach and the following go-around: https://bea.aero/fileadmin/user_upload/F-GSQJ_finalreport_EN.pdf

No it doesn't have one - there is no need really.  On the Airbus, the control movements on one side stick are not replicated on the other - therefore it's very difficult for one pilot to really be sure what the other is inputting to the controls.  On Boeings, the control inputs are replicated - therefore, by using physical force, one pilot can overpower the other's inputs.  It the 'bad' pilot is stronger (and 'fights' the other's inputs) he may still be able to put in the incorrect controls.

Boeing philosophy is to make pilots fly the airplane. The yoke inputs will be possible from either pilots during the whole flight, it is not  possible to cancel the input from either yoke. However, opposite inputs from both pilots will result the flight control deflection based on the deference of the force inputs (captain input 4kg and F/O input 3kg, the flight control input will be 1kg from captain yoke). With the same force inputs, will cancel each other's inputs and the flight will stay on its last position.


text:
Callsign includes the term 'with Kilo' ; What does that signify?
In FS-X I sometimes see with Kilo at the end of a Call-sign. For example the one from last night had

Mike Sierra Alpha Bravo with Kilo

What does With Kilo mean?

Listen to the tower also, they will probably be saying something on the lines of "current information Kilo"

Related, if not duplicate

It's just the ATIS version, so the tower and pilot can crosscheck they have the most recent weather/terminal information. They go up by one letter per version. So the next met release would be 'with Lima'. 'With information Kilo' is better than 'with Kilo'. Some airport terminal areas will also report the QNH for you, for your altimeter settings. This is on the ATIS/METAR report, but it can change quickly.

What that probably means is that the pilot is reporting that they have ATIS information kilo. Automatic Terminal Information Service (ATIS) is a radio broadcast on a specific frequency (often a local navaid like a VOR) which a pilot dials up to get weather and airport information before joining one of the airfield's frequencies. Each time the information is updated in a day the next letter of the alphabet is used; "information Kilo" means the information has been updated 11 times that day.
If the tower had to relay weather, runway in use and other instructions to everyone pilot who joined the frequency it would take loads of their time; ATIS is instead there so controllers can spend their time controlling. When a pilot introduces his/herself on frequency at an airfield they announce the latest ATIS they have so that the controller knows they have up to date information and they don't need it relayed.
From a phraseology standpoint just saying "with kilo" is okay. I usually say "with information kilo" because it makes sure that kilo isn't confused as being part of my callsign.

The first time I took my wife flying, in a two-seater, after we landed, she asked me, "Who is Charlie?"

Hahahaha @Flynn! She meant nothing to me honey, honest!

So... you can also expect “with Juliet” or “with Romeo?”

@RoboKaren Or perhaps "Yankee Papa Oscar with Whisky", oh dear...

Kilo? What are you saying, I've put on weight??

@GdD Nah, it's kilos, not pounds, so it's mass rather than weight. :)

@RoboKaren You could even hear "One Two Romeo with Juliet."

As Kennedy Steve regularly says, in response to "Delta 123 ready for taxi with Mike", "You and Mike can taxi for 23L via Alpha"

Now that's interesting!

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
Do the wheels of taxi-capable helicopters have power?
There are many big helicopters which seem to taxi just as good as any fixed wing aircraft, for example CH-47.
Do their landing gear wheels have power or they also taxi using thrust like their fixed wing counterparts?
If they do have power, are the taxi controls different from the standard controls?

Helicopter wheels do not have power. Taxiing is accomplished by using the thrust from rotors- for example, in case of CH-47, with rotors at normal rpm, the helicopter will have some forward speed (5-6 kt) with controls at neutral and thrust control rod at ground detent. Steering is usually using pedals (some helicopters have hydraulic steering) and there are, of course brakes (which are used to control taxi using differential braking in some cases).
As you mentioned CH-47, it is interesting to know that there are different ways to taxi the helicopter under different conditions. For example, according to the operator's manual,

Taxiing with two aft gear on the Ground
... Displace the cyclic stick aft approximately 2 inches and increase the thrust till the forward landing gear is off the ground the helicopter begins to move. Maintain directional control with the directional pedals. Control taxi by adjusting the thrust control rod.

and

Taxiing with power steering
... After the helicopter has started to roll, the thrust control rod should be lowered to the ground detent. This amount of thrust and braking will maintain a moderate taxi speed. ... Turns are initiated by slowly rotating the control knob a small amount and then gradually increasing the knob rotation until the desired turn is reached.

There are separate procedures for hover taxiing and water taxiing, though they don't make use of wheels.

I've seen 47's doing that 2-wheel taxi before and wondered why they did it that way. Now I know. +1

The wheels do not have power - there is no propulsion system linked to the wheels, they just spin freely.
Taxiing is achieved by adding just enough collective so that the helicopter starts moving, but not enough to lift it off the ground. A little forward cyclic also help.
To slow down, the main wheels have brakes, like fixed-wing aircraft.

Helicopters using wheeled landing gear do not have a drivetrain providing power to the wheels, though they are equipped with brakes.  The helicopter can taxi on them, similar to fixed wing aircraft, or they can hover taxi, as most helicopters do.  The primary usefulness in wheeled landing gear is to make it easier to tow and maneuver for parking, hangar storage, etc, while the engines are shut down.  Virtually all large helicopters use this kind of landing gear for these reasons.

MI-17s have wheel capability, but only utilizing thrust. No other system used for taxing. It uses main rotor to taxi ahead and tail rotor to turn left and right. Pneumatic available for braking.

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What is typical cruise altitude in the Himalayas?
An important tourist connection goes from Tribhuvan International Airport (VNKT) in Kathmandu, at 4,390 ft, to Tenzing-Hillary Airport (VNLK) in Lukla, at 9,334 ft. The mountains around Lukla quickly raise from south to north. Right around Lukla the ridges rise to about 15,000 ft, but the aircraft does not have to fly over these, since decent approach is only possible through the valley from the south and the ridges are somewhat lower further south. So does anybody know what is actual typical cruise altitude in that area?

I am sure I have no knowledge for reading charts but en-route charts for Nepal indicate something like F170 which I translate to FL170 or 17,000 ft. Pls correct me if I misunderstand it.
Here is the source

Thanks for the map. However, the B345/G348 that has the FL170 minimum is an IFR airway while the flights to VNLK are VFR. They may be using the KTM radial 94 drawn with thin line above, but I don't see any altitude mark on that one.

Agree that flights to VNLK are VFR. So I am out of luck here :)

You need to be between 13k - 9.1k ft for the Kathmandu to Lukla flight. This source would probably answer your question.

That is a simulator link; it's not clear whether the procedure is observed from reality or just guessed from map and simulator.

The simulators are expected to work by simulating real life situations I guess.!!

Except I've never seen a simulator that would be able to simulate hypoxia and altitude sickness, which is the limiting factor in this case.

While deciding the altitude range for the flight, and before putting it into a simulator, I think the developers would have taken into account that what is the Altitude that the pilots are currently using for the given flight path, and hence the problems of altitude sickness and hypoxia would be solved automatically.

If it was a training simulator, yes. But a hobby one can't be taken as reliable reference.


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Need help understanding how to decode BCDs and extract specific bits from ARINC 429 data
I do not have much background on this topic; I spent days reading documentation and trying to understand - but I am still completely lost.
I think I understand that the octal number (data label?) tells you the type of the data.
For example, if I have octal number 271, this means this is discrete data and can be BNR and/or BCD. More specifically, I have this data (BCDs):

1059072, when I convert to binary: 0001 0000 0101 1001 0000 0111 0010
2148546816, when I convert to binary: 0010 0001 0100 1000 0101 0100 0110 1000 0001 0110
1064192, when I convert to binary: 0001 0000 0110 0100 0001 1001 0010

I don't know how to map these binary values into the ARINC429 data word to get the correct 17th, 18th, 19th, 20th bit. Bits 9-10 are SDI, bits 22-29 are defined as spares (and so I think they are set to 0), 30-31 are SSM and 32 is parity.
So if bits 22-29 are defined as spares, I assume that this means the meaningful data exists in bits 11-21 of ARINC 429 data word, and the binary values above should be mapped into those. The problem is I have no idea how to map them, despite searching everywhere. I know that ARINC 429 bits are from MSB-LSB, so I know this should be taken into account when mapping by starting from the right side of the binary values, but the problem is I have no idea how to map them to correctly "fit" this range. Apparently the 17th-20th bits should be 0, but no matter how much I try I am not getting that.
To clarify, my issue is not what the bits signify, as this is clarified in the documentation I have. My issue is how does one fit a BCD into the appropriate ARINC429 format? For example, if a BCD is 40-bits in binary form, how does that even fit into ARINC 429 format in the "data field" portion, specifically, bits 11-21 (since 22-29 are spares and unused)?

That's a lot of unknowns, does reading this (and this answer) help clarify and reduce the scope of what is not clear?

The discrete data is going to be specific to the equipment you're receiving data from, there isn't a standard that says these bits mean this for label 271. You'll need to look at the documentation/ICD for the equipment you are receiving data from.

I have the documentation which says what the bits mean for this label, but the problem is I need to fit the binary values into the ARINC 429 format to determine whether bit 17 is 1 or 0, bit 18, 19, etc., and I don't know how to do that. For example, 1059072 gives 28 bits in binary form, but how can I convert this into ARINC 429 format by fitting it into bits 11-21  where I know the meaningful data is stored? I don't even know if this makes sense because of how little understanding I have, but I really don't understand how a 28-bit or 40-bit digit would fit into ARINC 429

If the label is discrete data, why are you trying to decode the value as a BCD number? The largest BCD number you can fit in the data field is 79999. It looks like the values you have provided are maybe provided by some tool rather than the raw 32 bit ARINC word.

Okay now that makes more sense as to why can't be mapped to fit into the data field. I'm sorry it's because when I read documentation I misunderstood that discrete data can be BNR or BCD, so I assumed from the number I have that it has to be BCD since it is not BNR. But now that you are saying the raw data values I have might be something completely different, then I seem to be on the completely wrong path anyway

Hi Anon, welcome on aviation.stackexchange.com. The ARINC 429 format is very aviation specific and thus considered on-topic. But then you are mapping integer values to binary representations in 3½ bytes, 5 bytes and 3½ bytes. Somehow I have the feeling this ends up in giving a generic course on binary data handling, rather than on aviation-specific formats. I think you need to start by understanding binary formats and bit shifting in general before diving in to ARINC. At least explain us how you are capturing this data, because it look like the tool chain may affect the outcome

Thank you. I really don't know, I received this raw test data which shows 1059072, 2148546816, 1064192. I was not given any further information regarding the format, I was just told it is hexadecimal, which I am not even sure if it is. This is a very frustrating task for me as it is not my specialty in any way, and I am expected to convert it to ARINC429 format and find bits 17-20.

I'm going to work off of the assumption that the values you have (1059072, 2148546816, 1064192) are the decimal representations of the raw 32 bit words received.
   1059072 => 00102900h == 00000000 00010000 00101001 00000000b
2148546816 => 80103900h == 10000000 00010000 00111001 00000000b
   1064192 => 00103D00h == 00000000 00010000 00111101 00000000b

Assuming the label has been zeroed out, and the hex value represents the entire label, the value 1064192 probably corresponds to the following layout.

Looks like discrete bits 21, 14, 13, 12, and 11 are set to me.

Thank you, I just wanted to let you know that your response solved the issue!

As stated in the comments section, the largest value in the data field of an ARINC 429 word with BCD is 79999. However, you could use the Williamsburg/Buckhorn protocol, which is basically an improvement to the ARINC 429 protocol, in order to be able to transmit more than 19 bits of data.
This is a bidirectional system (2 x ARINC 429), and the transfer unit is a "File". The file is divided into LDUs (Link Data Units), which are groups of 32-bit (ARINC 429) words. Files can include up to 255 words. Consequently, within LDUs, you can transmit information packages that exceed the nominal capacity of ARINC 429 words.
The Williamsburg/Buckhorn protocol operates as follows:
· First, there is the Handshake, where an RTS (Ready to Serve) word is transmitted, and the receiver replies with a CTS (Clear to Serve) word, allowing the transmission of the file.
· To begin the transmission of each file, an SOT (Start of Transmission) word is transmitted, indicating that a file is about to be transmitted. It includes information about the number of words within the LDU and the LDU number within the file.
· Then, each word within the LDU is transmitted until the end. Once all are sent, an EOT (End of Transmission) word is transmitted, indicating the LDU is completely sent. It also includes a CRC (Cyclic Redundancy Check) error-detecting code.
· An ACK is sent by the receiver.

As @selectstriker2 notes in comments, the largest value you can fit in the field as BCD is 79999. From a tutorial on the format (p. 14)

"Up to 5 subfields can be utilized to provide 5 binary values, with the
Most Significant subfield containing only 3 data field bits (for a maximum binary value of 7). If the Most Significant digit is greater than 7, bits 27-29 are padded with zeros and the second subfield becomes the Most Significant digit allowing 4 binary values instead of 5 to be represented."

The format is deliberately pretty flexible, allowing for BCD, binary, and a mix of the two (or other uses entirely for the field). See pages 13-15 of the tutorial linked above for different options.
I don't think I'm able to answer the question as to how to represent a number larger than 79999 in this format, but given the discussion in the comments above I'm not sure that's needed.

One function of ARINC429 messages that I have seen before is that of "Member System Identification" where a specific unit reports the serial numbers, software identifiers etc as part of a "stream" of ARINC429 words.
In each message 2 bytes of data is sent along with an index starting at 0.
For each subsequent 2 bytes of data sent the index is incremented by 1 and will restart at 0 when the sequence starts again.
For your BCD problem you could send two digits each message and similar to the scheme outlined already, use an index field to indicate what position within the BCD value these two digits represent.
If you want to send 123456, the messages would be
BCD1: 1 BCD2: 2 Index:0
BCD1: 3 BCD2: 4 Index:1
BCD1: 5 BCD2: 6 Index:2

Then starting again with
BCD1: 1 BCD2: 2 Index:0


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Would the solid material inside an airship displace air and be counted towards lift?
The hydrogen inside an airship has a mass that is approximately 14 times lower than the mass of air and this difference results in lift.

However the solid material inside an airship including the frame, skin, walkways, gasbag material etc. would also displace air.  Would the air that these materials displace also be counted towards lift?  I'm not sure.
If the extra displacement is counted towards lift is there any reasonable estimate as to how much space the solid material might fill?  1%, 2%, 5%?
A U Class Zeppelin has an outside volume of approximately 59,000 cubic meters.  However if 2% of this volume was solid material that's 1,180 cubic meters of atmosphere displacement or an extra 1,445 Kg of lift.  Although not decisive I'm sure that any little bit helps.

"and this [density] difference results in lift" That's inaccurate, at best. The lift comes from the hydrogen (or the frame, or anything) having volume, regardless of the mass. However, the difference in density results in positive buoyancy, meaning that lift is greater than the weight. Once you make that split clear (volume + density of surrounding fluid -> lift, mass + gravity -> weight) the answer should be quite intuitive.

Everything that displaces air is affected by buoyancy. Fun fact: when calibrating equipment that can measure weight/forces in the hundreds of tonnes you have to take into account the air displaced because the displaced air "lifts" the calibration weight: https://youtu.be/_k9egfWvb7Y?t=231

Short answer yes.  Clearly any solid material must displace an equal volume of air.  However, the mass of a structure is typically determined by measuring its weight, and that is typically measured in air and so the buoyancy provided by the atmosphere is already factored in.  For dense materials such as metals this is typically negligible, but clearly for low-density materials such as hydrogen it is important, where a litre of hydrogen has a true mass of around 80mg but a weight in free air of approximately -10mN.

It would, but it is so little it is not noticeable
Duraluminium has a density of 2780 kg/m3, plain air has a density 1.3 kg/m3. So the buoyancy is in the order of 0.05%. The dry weight of the Hindenburg for example was 100 tons, meaning that the buoyancy of the solid material is about 50 kg.
This is so little that other effects on lift — i.e. changes in temperature, internal gas pressure, external atmospheric pressure, dynamic lift from relative wind speed, ballasting, spending fuel, and more — will completely drown out this effect.

It's also worth noting that the buoyancy is already accounted for -- when you stick the uninflated Hindenburg on a scale to weigh it, the number it produces is 50 kg lower than it would be in a vacuum.

@Mark -- absolutely-- of course you could argue that what you read on the scale is not really "weight", because it is not exactly the same as mass * gravity

@quietflyer What you read on a scale is called Apparent Weight.

Buoyancy is best defined as weight of displaced air minus weight of the stuff that is displacing the air.  If the "stuff" doing the displacing is heavier than air, then the buoyancy contributed by that displacement is negative rather than positive.  Still, if we want to calculate total buoyancy and we know total mass or total weight, strictly speaking we should not neglect the weight of the volume of air that is displaced by the heavy parts of the airship.  As other answers have pointed out, the resulting contribution to buoyancy is negligible, but not zero.
This answer is using the strict physics definition of "weight", i.e. mass times gravity.  If by "weight" we mean what we read when we put an object on a scale, which is called "Apparent Weight", then the buoyancy created by the displacement of air is already accounted for, at least for the atmospheric conditions prevailing at the location of the scale.  The fact that in reality we almost never consider the difference between these two kinds of "weight" in the context of heavy metal objects, shows how slight the difference actually is.

What are you people suggesting, here? Metal displaces the same volume of air and that creates lift? A hollow tank with thin sides might but a sizeable chunk of metal?

"...displace more air per unit volume than..." WHAT?  A think of X volume displaces that volume of air, irrespective of the thing's density. All reasoning that follows a misstatement like this is highly suspect.

@RalphJ -- I edited to this "Note that airplanes are much denser than airships, so they displace MORE air (per unit volume enclosed by the outer surface of the aircraft) than an airship with empty gas cells does. Of course that "advantage" is completely offset by the weight of the stuff that is doing the displacing.", then decided to just delete the first two sentences entirely, not really essential to the main point, and leads to useless arguments as to whether or not one is intending to include the volume occupied by the air inside the aircraft.

@RobbieGoodwin Yes. If you put a cubic metre of iron on a scale, in a vacuum, it will read 7874 kg. If you do it in air at STP, it will be 1.3 kg lighter, because of the buoyancy from the cubic metre of air it displaces.

I don't know the right term but do those clearly correct conclusions not depend on some kind of ’relativistic’ association?
Since you lead me to think that way, don't they depend on the displacement, not any intrinsic property of iron or air?
Don’t those clearly correct examples ignore the possibility of first placing the iron on the scale in vacuum, then adding air to the system?
Wouldn't that result in the same volumes and densities of iron and air, with no displacement?
At that point I’m lost and I hope you can show me the way, even if only by pointing to some useful texts…

Of Oscar Bravo, I ask how you've explained RalphJ's query, rather than compounding it?


text:
What's the highest altitude ever achieved by a (rocket-?)plane for level flight?
As probably most of us know, the SR-71 Blackbird holds the altitude record for leveled flight for (manned) jet planes (and ground-launched planes) at 90,000 ft MSL. However, the very altitude record in leveled flight is probably held by a rocketplane, such as the Bell X-1 or the North American X-15. Is there an altitude record for leveled flight that surpassed that of the Blackbird? What's the record for the highest horizontal flight by a rocket (or any other type of) plane? May include unmanned ones.
Edit: To make it clear, my question asks for the altitude record of a winged aircraft that could sustain this altitude aerodynamically. But Abdullah answered my question anyway, it was the NASA Helios propeller craft (which looks a bit weird but still is a winged aircraft) that reached and sustained an altitude of 96900 ft (29,500 m). Wikipedia says this is the altitude record for aerodynamic horizontal flight.

Welcome to Aviation.SE! Could you clarify what exactly you would count as a rocket-plane? Would the space shuttle count?

@Bianfable Thank you. No, because the Space Shuttle didn't fly aerodynamically leveled with engine on. The point is that the rocket-engine is on while flying. So no gliding unless the altitude can be maintained regardless (like by a sailplane).

@Abdullah Thank you. That's actually an answer rather than a comment since the link states it's the highest winged craft in leveled flight ever. Why would it be difficult for rocketplanes to fly horizontally?

@Giovanni: "Why would it be difficult for rocketplanes to fly horizontally?" – It's not difficult, it just doesn't make sense. If you're aerodynamically flying horizontally, then you don't need a rocket. If you need a rocket that means you expect to be flying where there's no oxygen, but then you are going up not level, and you're not flying aerodynamically.

@JörgWMittag But if a pilot wanted to fly horizontally at too high altitude for whatever reason, they'd need a rocketplane because jet planes can't fly there due to the lack of oxygen as you point out, and propeller planes don't get fast enough to get too high because they shouldn't break the sound barrier.

@Giovanni if one is really going to go that high, then it would be better to just design a jet engine that can breathe up there. It's not physically impossible or impractical anyway.

@Giovanni --it's not clear what exactly would disqualify the Space Shuttle in orbit from the question.  I think you need to specify non-oribital horizontal flight.

@quietflyer In orbit it doesn't fly but float through (near-)vacuum in free fall, and its nose doesn't need to have horizontal pitch. Also, this is aviation SE, not space SE. But feel free to understand this question as "other than the Space Shuttle and the Buran". (:

@Giovanni, would a sub-orbital ICBM meet your definition of horizontal flight in an unmanned rocket?  If not, why not?

@MichaelHall the trajectory would only be horizontal instantaneously, at the exact peak of the arc, right?

@Giovanni -- wouldn't "sustained horizontal flight" or something to that effect be clearer than "levelled"?  I'm assuming it's the flight path not the pitch attitude that you actually want to specify.  (Or maybe both?)  Plus the issue of whether instantaneously level is sufficient--?  At present the question is somewhat unclear.

@quiet flyer, yes, but duration at "level" wasn't specified, plus an ICBM flies a rather shallow trajectory at roughly 5:1 horizontal to vertical.  And at scales where "level" is not the same as "straight":  i.e. Curvature of the earth is a factor.  (even more so than in other questions insinuating that in a small plane downforce is needed to follow the earth and avoid flying into space...)

"even more so than in other questions insinuating that in a small plane downforce is needed to follow the earth and avoid flying into space"-- that such a thing is not needed, is proof that the earth isn't round --  :)

@MichaelHall An ICBM doesn't qualify because it's not a plane (not a winged aircraft). It's not even an aircraft at all but a spacecraft actually. My question is concerning aerodynamic sustaining of altitude.

You should go ahead and make an answer out of the Helios and accept it. Not sure why the comment was deleted.


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How can I calculate 'Max aircraft Load Factor' and 'Max aircraft Speed' when flaps are fully extended on a civil aircraft?
I am trying to calculate the critical loading conditions for Flaps (in order use them inside my Finite Element Analysis to, determine if the Flaps will be able to bear these critical loads) during the design phase of a civil aircraft. Below shows the generic V-N diagram for most of the civil aircrafts.

Now, I have the CFD results available for multiple combinations of angles of attack of the aircraft, with the deflection angle of the flap. I have to choose a couple, to input into my structural analysis of the flaps. How to determine the most critical loading conditions (Aircraft's angle of attack and Flaps' deflection at that angle of attack) for the flaps?
Now what is understood is that the greater the flap extension, the more overall Cl of the wing/aircraft (for the same angle of attack), and this will cause flaps to take more load during the flight (assuming that the extra load due to increase in Cl in just coming from Flaps only, and not from the actual wing).

Therefore, when the flaps are deployed to full extension, that is when the flaps should take the maximum load. How should I determine and calculate the load factor at this maximum flaps deflection, and also maximum flaps extended speed for this case? If these both are known, then the angle of attack of the aircaft can be found, and hence that specific CFD result can be implemented in my structural analysis of the flap.
Is there a limit on the load factor that beyond which the flaps cannot be deployed (or fully deployed) during flight? Is it possible for the flaps to be deployed fully when the aircraft is undergoing limiting load i.e. 4.4g and -1.8g (as shown in the V-N diagram above)? Or a completely new and different V-N diagram should be built for the aircraft, where flaps are completely deployed?

I think you are approaching this backwards.  One computes the loads (and adds the desired safety margin) to determine the envelope boundaries.  I.e you would use the FE analysis to determine the structural integrity and from that you set the envelope.   The flaps will therefore be able to bear the critical loads because you’ve set them such that they will.

But that is the problem. For which loading conditions should I conduct my FEA? I mean there are hundreds of combinations of A.o.A of the aircraft with the flap deflection, and there might be a chance that some might even not be possible during the aircraft's life, so if I choose them and size my flaps in accordance with these, then I am essentially over-sizing the flaps.

Everthing can become alot easier to work with if I know what is the maximum load factor that can be used with the flaps fully extended, then I already know the max/min Cl of the aircraft (when flaps fully extended) and I can then know the max/min velocity of the aircraft when flaps fully extended.

Flap size is determined by performance goals for takeoff and landing, not by structural limits.  The structure is designed to take the load required.

I think you are misunderstanding me. I never said that I need to size the flap (as in I need to size the surface area, span and chorlength of the flaps). What I meant is the thickness. If you are a bit familiar with the structures, then you would know that the thickness of structures will vary the stresses that the structure is undergoing, when subjected to transverse loading (as like lift).

The red zone in the graph is for high speed & load factor combinations, it is the zone where structural failure will occur. Trailing edge flap deflection is only allowed at limited airspeed, and the flap structural support is designed for those particular airspeeds only, with the usual structural safety margin of 1.5 of passenger aeroplanes (also mentioned in this question).
An example, from the B737 technical site:, Trailing Edge Flaps

Trivia: Although the flap placard limit speeds are different for each 737NG variant, the structural limit speed for the flaps is equal to the placard speeds (175k – F30, 162k – F40) for the heaviest variant (737-800/900). The Flap Load Relief trigger speeds (176k – F30, 163k – F40) are set to allow all variants to fly to the structural limit speed without system activation. Setting lower flap placard speeds for the –600 and –700 variants allows for greater service life of flap components due to the larger margins to the structural design speed.

So this is the Structural Limit Speed with extended trailing edge flaps.

From the V-N diagram, the maximum load factor at this speed will follow.
Maximum $C_L$ indeed follows from the lift curves, with the stall AoA taken as maximum. Leading edge devices  need to be considered as well, since they allow for higher AoA, refer to the graph below from Torenbeek's Synthesis of Subsonic Airplane Design.


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PRIM 1 FAULT prior to ETOPS entry, Reroute or Continue?
As per the Minimum Equipment List (MEL) you cannot dispatch a plane for ETOPS if it has PRIM 1 FAULT (Flight computer fault) However if this fault appears in flight just prior to entering the ETOPS/EDTO segment should you still continue or fly a non ETOPS/EDTO route? Since the MEL is only referred to prior to flight, I cannot refer to this document to justify not flying the ETOPS route. There is a requirement though for twins that all EDTO significant systems should be operational before conducting an
ETOPS/EDTO flight. I haven’t seen an EDTO specific significant systems list only the general list published by ICAO which includes almost all the systems of the plane. The question is, would PRIM 1 fault, which was considered a NO GO on the ground still be considered an EDTO significant system in flight wherein it would only result to a loss of a pair of spoilers and computer redundancy? I hope somebody here would share their EDTO significant systems list.

Welcome to Aviation.SE! Could you please add which aircraft you are talking about? You mention ECAM, so I guess an Airbus, but the exact model would probably help answering the question.

Don't you have a training captain or company representative you can ask this question?

I'd say just go for it, continue w/ ETOPS.  Let me know if you took my advice and how it all worked out!

Welcome to aviation.SE! I don't know that there's any clear answer to this, because each airline's OpSpecs (or equivalent) may have different guidelines. Even if the PIC always makes the final decision, I assume they'll follow the OpSpecs unless there's a good reason not to.

Thank you for all the responses. I just want know what other pilots think and I appreciate it. I asked this question because it was given in the simulator. As for the scenario above, you haven’t started ETOPS OR EDTO yet

Since you are already airborne, the MMEL doesn't come into it. The system was normal when you dispatched.  What applies is the QRH (Quick Reference Handbook).  You should look for that particular message in the QRH in the section on status messages (I assume that fault messages are white status messages in Airbus-land).
If there are any restrictions on ETOPS operations with a fault that comes on while airborne, there will be a notation of some kind to that effect, referenced or attached to that message in the QRH, that you have to divert or take some sort of mitigating action before or after entering ETOPS conditions.  If not, you're good to go.
The MMEL is based on an analysis of risk exposure related to potential follow-on effects following a departure with a degraded system (that is, a second failure of the remaining component of the system in flight that renders the entire system inoperative or operationally compromised).  The risk level prior to departure is higher than the risk level while airborne, because as a general rule, double failures on the same flight are assumed to be extremely improbable.
And, obviously, you should consult with someone in authority at your airline instead of going on the statements of anonymous nobodies on the intertubes...